1. Field of the Invention
The present invention relates to an imprint device and a microstructure transfer method for transferring a fine-patterned structure of a stamper to a surface of a patterned material.
2. Description of the Related Art
Microfabrication of semiconductor integrated circuits has progressed and there has been improvement in the accuracy for forming a pattern of a semiconductor integrated circuit by, for example, the photolithography device in order to perform the microfabrication process. On the other hand, a pattern for the microfabrication process is almost as small as a wavelength of an exposure light source, and therefore the microfabrication process is approaching to a limit for the high accuracy of the pattern formation. Therefore, the electron beam lithography device, which is a type of the charged particle beam device, has been used instead of the photolithography device in order to obtain the higher accuracy of the pattern formation.
The pattern formation by the electron beam lithography device is different from a pattern formation by a batch exposure method using a light source such as i-line, an excimer laser or the like, and in the electron beam lithography device an exposure (drawing) time of patterns increases according to the increasing of the patterns to be drawn by the electron beam. Therefore, the time required for the pattern formation becomes longer as the integration of the semiconductor integrated circuit increases. As a result, a throughput becomes considerably lower.
For speeding up the pattern formation by the electron beam lithography device, there has been development in batch drawing radiation method, in which the electron beam is applied with various types of masks combined. However, the electron beam lithography device, which uses the batch drawing radiation method, increases in size and requires a mechanism for controlling a position of a mask with higher accuracy, thereby increasing the cost of the device.
Furthermore, there has been known as another technique for the pattern formation an imprint technique for transferring a surface structure of a predetermined stamper on a patterned material by pressing the stamper against the patterned material. In the imprint technique, the stamper has a fine-patterned portion (surface structure) corresponding to a fine-patterned portion of a pattern to be formed on the patterned material. The stamper is pressed against the patterned material, which is produced by forming a resin layer on a prescribed substrate. Thereby, a microstructure having a fine pattern width of less than or equal to 25 nm is transferred to and formed on the resin layer of the patterned material. The resin layer having the pattern transferred thereto (hereinafter referred to as a pattern formation layer) includes a thin film layer formed on a substrate and a pattern layer formed on the thin film layer and having projections. There has been consideration for applications of the imprint technique in the pattern formation for a record bit in a high-capacity recording medium or a semiconductor integrated circuit. For example, a substrate for a high-capacity recording medium or a semiconductor integrated circuit may be manufactured by etching an exposed portion of a thin film layer at a concave portion of the pattern formation layer, and a portion of a substrate in contact with the portion of the thin film layer with a convex portion of the pattern formation layer formed by the imprint technique as a mask. The accuracy for the etching process of the substrate is affected by a thickness distribution of the thin film layer in the surface direction. More specifically, for example, a thickness variation of the thin film layer in the surface direction is such that the difference in thickness between the thickest portion and the thinnest portion of the thin film layer is 50 nm. When the patterned material having such a thin film layer is etched in the depth of 50 nm, the substrate in contact with the thin portion of the thin film layer is etched while the substrate in contact with the thick portion of the thin film layer may not be etched. Therefore, the thickness of the thin film layer formed on the substrate needs to be uniform in order to maintain a predefined accuracy of the etching process. Namely, the thickness of the resin layer formed on the substrate needs to be uniform in the surface direction in order to form the thin film layer having the uniform thickness.
U.S. Pat. No. 6,696,220 discloses a conventional imprint device including a stamper having a flat surface on which a fine pattern is formed, and the flat surface of the stamper is mechanically pressed against the patterned material, thereby transferring the fine pattern to the patterned material. In the imprint device, the fine pattern is formed on the flat surface of the stamper, and therefore it is possible to apply a uniform pressure to a patterned region, to which the fine pattern of the stamper is transferred, of the patterned material. When the uniform pressure is applied to the patterned region, the resin layer having the uniform thickness is formed on the patterned material. That is, when the fine pattern is formed on the patterned material with the resin layer having the uniform thickness, the thickness of the pattern formation layer is uniform and thereby the thickness of the thin film layer of the pattern formation layer is uniform, too.
However, the above-described imprint device requires an adjustment mechanism capable of aligning the stamper and the patterned material parallel to each other with high accuracy, thereby making a configuration of the imprint device complicated. Furthermore, in the imprint device, there is a limit on the size of the stamper to be able to be made flat, and it is difficult to form the pattern formation layer (thin film layer) having the uniform thickness by pressing a larger size of the patterned region against the stamper at one time.
For example, Japanese Laid-open Patent Application Nos. 2003-157520 and 2005-52841 disclose an imprint device, in which a patterned material and a stamper are pressed against each other on a stage through an elastic material. United States Patent Publication No. 2003/189273 discloses an imprint device in which a liquid is sealed in a cavity provided on a back surface of a stamper or a patterned material. Furthermore, U.S. Pat. No. 6,482,742 discloses an imprint device in which a stamper and a patterned material are disposed within a vessel, the internal pressure of which is adjusted.
In the imprint devices of the above-described patent references, however, a pressure distribution between the surfaces of the stamper and the patterned material is uniform when the stamper and the patterned material are pressed against each other. Therefore, it is difficult to sufficiently spread the resin between the stamper and the patterned material when the patterned region is larger and the thin film layer is thinner. In this case, the stamper and the patterned material can be damaged when the stamper is pressed against the patterned material with a higher pressure to spread the resin between the stamper and the patterned material.